Based on the fact of that the 3C products are rising and developing, continuously. The input devices such as keyboard or mouse of these consumer products are replaced by the touch panel gradually. The touch panel technology provides a friendly interface to allow a user may operate a computer or electronic products more convenient and easier than ever. Touch panels are input devices for operating an apparatus by directly touching a display screen of a liquid crystal display device or the like with a finger, a purpose-built stylus or the like, and include a display which displays operation details and the like, and a detection means which detects the position (coordinates) of a portion of the display screen of the display touched with the finger or the like. Information about the touched position detected by the detection means is sent in the form of a signal to the apparatus, which in turn performs an operation and the like displayed on the touched position. Examples of the apparatus employing such a touch panel include ATMs in banking facilities, ticket vending machines in stations, portable game machines, and the like.
Additionally, the applications of the touch panels are widely spread, the field of such devices includes but not limited to portable communication or information devices (such as personal digital assistant, PDA), electronic dictionaries, handsets, MP3s, digital players, or global positioning systems (GPSs), or other small size electronic devices, financial/commercial system, hospital register system, monitoring and control system, information system and computer assisted instruction system, etc. The convenience of operation is upgrade owing to it's friendly operation interface.
The above mentioned application usually utilizes single-touch panel or writing pad as an input device. However, the single-touch panel or writing pad only can detect a single touch-point at one time. In other words, it merely can receive or process an identification position of the touch signal at each time.
U.S. Pat. No. 4,233,522 has disclosed a capacitive touch panel comprising an array of touch sensitive switch cells. Each switch cell includes a first and a second pair of series connected capacitors energized by a common signal source, the array of switch cells being arranged so that the first pair of capacitors are connected in first groups of switch cells, such as rows, to a corresponding first plurality of signal detectors, and the second pair of capacitors are connected in second groups of switch cells, such as columns, to a corresponding second plurality of signal detectors, the junctions of each pair of capacitors of a single switch cell being selectively coupled to ground by the body or other touch capacitive means for actuating a selected switch cell.
In order to detect the location where a finger or a stylus touches the touch panel, a variety of capacitive touch panel techniques are developed. An example is U.S. Pat. No. 6,970,160, which discloses a lattice touch-sensing system for detecting a position of a touch on a touch-sensitive surface. The lattice touch-sensing system may include two capacitive sensing layers, separated by an insulating material, where each layer consists of substantially parallel conducting elements, and the conducting elements of the two sensing layers are substantially orthogonal to each other. Each element may comprise a series of diamond shaped patches that are connected together with narrow conductive rectangular strips. Each conducting element of a given sensing layer is electrically connected at one or both ends to a lead line of a corresponding set of lead lines. A control circuit may also be included to provide an excitation signal to both sets of conducting elements through the corresponding sets of lead lines, to receive sense signals generated by sensor elements when a touch on the surface occurs, and to determine a position of the touch based on the position of the affected bars in each layer.
U.S. Pat. No. 7,030,860 has disclosed a transparent, capacitive sensing system particularly well suited for input to electronic devices. The capacitive sensor can further be used as an input device for a graphical user interface, especially if overlaid on top of a display device like an LCD screen to sense finger position and contact area over the display. Furthermore, International Publication Number WO 2009/090534 A2 has disclosed “Device for quantifying an electric unbalance and touch detection system incorporating it”; and U.S. Pat. No. 8,144,132 B2 has disclosed “Multipoint sensing method for capacitive touch panel”.